Disclosed herein are ink jet printheads having fluorinated poly(amide-imide) copolymer front face coatings.
Ink jet systems include one or more printheads having a plurality of jets from which drops of fluid are ejected towards a recording medium. The jets of a printhead receive ink from an ink supply chamber or manifold in the printhead which, in turn, receives ink from a source, such as an ink reservoir or an ink cartridge. Each jet includes a channel having one end in fluid communication with the ink supply manifold. The other end of the ink channel has an orifice or nozzle for ejecting drops of ink. The nozzles of the jets can be formed in an aperture or nozzle plate having openings corresponding to the nozzles of the jets. During operation, drop ejecting signals activate actuators in the jets to expel drops of fluid from the jet nozzles onto the recording medium. By selectively activating the actuators of the jets to eject drops as the recording medium and/or printhead assembly are moved relative to one another, the deposited drops can be precisely patterned to form particular text and graphic images on the recording medium. An example of a full width array printhead is described in U.S. Pat. No. 7,591,535, the disclosure of which is totally incorporated herein by reference. An example of an ultra-violet curable gel ink which can be jetted in such a printhead is described in U.S. Pat. No. 7,714,040, the disclosure of which is totally incorporated herein by reference. An example of a phase change ink which can be jetted in such a printhead is the Xerox Color Qube™ cyan solid ink available from Xerox Corporation. U.S. Pat. No. 5,867,189, the disclosure of which is totally incorporated herein by reference, describes an ink jet printhead including an ink ejecting component which incorporates an electropolished ink-contacting or orifice surface on the outlet side of the printhead. Additional examples of ink jet printheads are disclosed in U.S. Pat. Nos. 7,934,815, 7,862,678, and 7,862,160, the disclosures of each of which are totally incorporated herein by reference. Thermal ink jet systems, in which the expansion of a bubble forces a droplet of ink out of the nozzle, are also known, as disclosed in, for example, U.S. Pat. Nos. 4,601,777, 4,251,824, 4,410,899, 4,412,224, and 4,532,530, the disclosures of each of which are totally incorporated herein by reference. Also known are acoustic ink jet printing systems, as disclosed in, for example, U.S. Pat. Nos. 4,308,547, 4,697,195, 5,028,937, 5,041,849, 4,751,529, 4,751,530, 4,751,534, 4,801,953, and 4,797,693, the disclosures of each of which are totally incorporated herein by reference. Other known droplet ejectors include those of the type disclosed in, for example, U.S. Pat. No. 6,127,198, the disclosure of which is totally incorporated herein by reference.
One difficulty faced by ink jet systems is wetting, drooling, or flooding of inks onto the printhead front face. Such contamination of the printhead front face can cause or contribute to blocking of the ink jet nozzles and channels, which alone or in combination with the wetted, contaminated front face, can cause or contribute to non-firing or missing drops, undersized or otherwise wrong-sized drops, satellites, or misdirected drops on the recording medium, and thus result in degraded print quality.
Current printhead front face coatings are often sputtered polytetrafluoroethylene coatings. When the printhead is tilted, some inks do not readily slide on the printhead front face surface. Rather, these inks flow along the printhead front face and leave an ink film or residue on the printhead which can interfere with jetting. For this reason, the front faces of UV and solid ink printheads are prone contamination by UV and solid inks.
In some cases, the contaminated printhead can be refreshed or cleaned with a maintenance unit. Such an approach, however, introduces system complexity, hardware cost, and sometimes reliability issues. Contamination of the printhead can also be somewhat minimized by adopting purging procedures. These procedures, however, can consume time and use excessive amounts of ink.
In the case of inks such as phase change and UV curable gel inks, contamination of a printhead front face can also be minimized by providing an oleophobic low adhesion front face coating that does not wet significantly with ink ejected from nozzle openings of the printhead. When heated to temperatures typically encountered during printhead fabrication processes, however, the surface property characteristics of many known oleophobic low adhesion coatings degrade to the point that they cannot be relied upon to minimize contamination of the printhead front face.
A need thus remains for an improved printhead front face design that reduces or eliminates wetting, drooling, flooding, or contamination of ink, including UV or solid ink, over the printhead front face. In addition, a need remains for an improved printhead front face design that is ink phobic and robust to withstand maintenance procedures such as wiping of the printhead front face. Further, a need remains for an improved printhead that is easily cleaned or in some cases that is self-cleaning, thereby reducing or eliminating hardware complexity, such as the need for a maintenance unit, reducing run cost and improving system reliability. Additionally, a need remains for materials for coating printhead front faces that, while enabling excellent cleaning and, in many cases, self-cleaning properties, also is sufficiently robust to survive both the temperature and pressure conditions encountered during printhead fabrication and the temperature conditions encountered during printer operation without degradation. There is also a need for printhead front face coatings that exhibit improved anti-scratch properties. In addition, there is a need for printhead front face coatings that exhibit improved chemical resistance to varied chemical environments.